Many different diamond composites have been disclosed in literature, and their advantages as a material for use in the cutting, turning, drilling and similar of hard materials, in particular metal alloys such as steel but also rock and similar materials, have been identified and resulted in the use thereof in such application. Of importance to the performance of the diamond composites is their diamond density which is strongly dependent on the packing of the diamonds and thus also the diamond particle size distribution. Generally, a diamond composite may be referred to as a polycrystalline body possessing substantial abrasiveness and hardness and low or negligible porosity comprised from about 40 percent of volume by diamond crystals. Apart from diamond particles, diamond composites may also comprise a binder, positioned between individual diamond particles in the diamond composite, where it may form a matrix-like structure. A common binder in diamond composites has been silicon carbide, and different methods have been suggested to generate or introduce the silicon carbide into a mass or body of diamond crystals. One such method is referred to as infiltration. Infiltration may be achieved by means of a silicon source that is positioned adjacent to a body of diamond particles and subjected to heat such that it will melt and infiltrate the body of diamond particles. The silicon source may be referred as an infiltrant.
As an alternative, the silicon source may be premixed with the diamond particles before heat is applied to the mass of diamond particles and silicon source thereby formed. In the mass or body of diamond particles the molten silicon source reacts with carbon, either carbon of the diamond particles and/or carbon added to the body specifically for reacting with the silicon source, and forms silicon carbide that will act as a binder in the diamond composite thereby formed. Combinations of use of an infiltrant and premixed silicon source have also been suggested by prior art. In U.S. Pat. No. 7,008,672 B2 using a low pressure infiltration route, the importance of a high heating rate above 1000° C. to avoid a complete graphitisation of the small diamond particles prior to the infiltration is described to be able to achieve a high diamond density and maintain small diamond particles in the sintered parts.
As mentioned above, temperature is one important factor when producing a diamond composite. In order to arrive at a dense diamond composite, a so-called compact, an elevated pressure is also suggested. Elevated density may be achieved in different ways. For example, a mass of polycrystalline diamond particles may be positioned in juxtaposition with a body of silicon. This diamond-silicon assembly is put into a high pressure-high temperature, HPHT, apparatus in which a punch or the like is used for subjecting the diamond-silicon assembly to a very high pressure (for example 15-50 kbar) while, simultaneously, a temperature high enough for melting the infiltrant and causing the above-mentioned reaction between silicon and carbon is applied to the same assembly. Prior art documents, such as U.S. Pat. Nos. 4,874,398, 5,106,393, US 20130167447 and U.S. Pat. No. 5,010,043 all disclose so called HPHT (High Pressure High Temperature) processes in which a very high pressure is applied to a powder or a preform of diamond, followed by the application of an elevated temperature that causes the melting of the infiltrant. A HPHT-process, in general, provides a sintered material with very high diamond content (>70 vol %). However, the problem with HPHT-process, due to the high pressure, is that there is significant limitations in the amount and size of the bodies that may be produced.
Also, there have been suggested manufacturing diamond composites using hot pressing, e.g. U.S. Pat. No. 4,168,957. However, these processes are difficult to adapt for the complex shaped objects in industrial scale.
There has also been suggested by prior art to make use of the so-called Hot Isostatic gas Pressure, HIP, technique in order to apply the heat and pressure required to infiltrate a mass of diamond particles with a an infiltrant and generate the reaction in which the infiltrant forms the requested binder, normally silicon carbide. The use of HIP could be a way of achieving improved production capacity of diamond composite components of rather complicated design, and it is therefore of interest to suggest a HIP process which results in a dense diamond composite component that could be used in applications such as the turning, drilling and cutting of hard materials in general and metals and rock in particular. “HIP-Sintered Composites of C (Diamond)/SiC”, by M. Shimono and S. Kume, published in J. Am. Ceram. Soc., 87 (4), 752-55 (2004) discloses a HIP process, in which a mass of diamond particles is premixed with a silicon source with which it is reacted in order to generate a diamond composite component comprising diamond particles and a silicon carbide binder. A capsule made of SiC covered by a glass tube is used, and diamond particles and silicon particles is filled as a mixed powder into the capsule before the application of heat and elevated pressure of the HIP process is initiated. However, the described process does not mention the possibility of using a pre-compacted green body of diamond particles enclosed by a silicon infiltrant and how to possibly adapt the choice of capsule material with regard thereto in order to obtain a denser final component. The use of pre-compacted green bodies instead of loosely packed powder will be of great importance for accomplishment of a more efficient production process in which larger number of components of relatively complicated design can be produced.